There has been a major effort in recent years to discover new drug compounds that act by stimulating certain key aspects of the immune system, as well as by suppressing certain other aspects (see, e.g., U.S. Pat. Nos. 6,039,969 and 6,200,592). These compounds, sometimes referred to as immune response modifiers (IRMs), appear to act through basic immune system mechanisms known as toll-like receptors to induce selected cytokine biosynthesis and may be used to treat a wide variety of diseases and conditions. For example, certain IRMs may be useful for treating viral diseases (e.g., human papilloma virus, hepatitis, herpes), neoplasias (e.g., basal cell carcinoma, squamous cell carcinoma, actinic keratosis), and TH2-mediated diseases (e.g., asthma, allergic rhinitis, atopic dermatitis), and are also useful as vaccine adjuvants. Unlike many conventional anti-viral or anti-tumor compounds, the primary mechanism of action for IRMs is indirect, by stimulating the immune system to recognize and take appropriate action against a pathogen.
Many of the IRM compounds are imidazoquinoline amine derivatives (see, e.g., U.S. Pat. No. 4,689,338), but a number of other compound classes are now known as well (see, e.g., U.S. Pat. Nos. 5,446,153; 6,194,425; and 6,110,929).
Pharmaceutical compositions containing IRM compounds are disclosed in U.S. Pat. Nos. 5,238,944; 5,939,090; and 6,425,776; European Patent 0 394 026; and U.S. Patent Publication 2003/0199538. The IRM compound, 1-(2-methylpropyl)-1H-imidazo[4,5-c]quinolin-4-amine, has been commercialized in a topical formulation, ALDARA, for the treatment of actinic keratosis, basal cell carcinoma, or anogenital warts associated with human papilomavirus.
However, providing therapeutic benefit by topical application of an IRM compound for treatment of a particular condition at a particular location or of a particular tissue can be hindered by a variety of factors, such as, for example, chemical degradation of the IRM compound and/or other ingredients, and physical instability of the composition (e.g., separation of components, thickening, precipitation or agglomerization of active ingredient, and the like).
Therefore, there is a continuing need for new and/or improved IRM formulations.